1. Field of the Invention
The present invention relates to a positioning system, an IC chip for positioning, a positioning method, and a positioning program for estimating the position of a receiver.
2. Related Background Art
Positioning of receivers using a global positioning system (GPS) or Galileo is known technology. Such systems perform positioning on the basis of the distance from a satellite (which may also be a pseudo-satellite), which is a positioning signal transmitter, to a receiver. Another positioning method referred to as a hybrid method is also known which uses signals from a satellite and signals from a mobile communication network at the same time.
With these positioning methods, the distance from a satellite to a receiver is calculated on the basis of the transmission time and the time of receipt of a positioning signal sent from the satellite to the receiver, and calculation for the positioning is performed using the calculated distance. If the distances from a plurality of satellites to a receiver and the positions of the satellites are accurately calculated, the position of the receiver can be determined through calculation of the intersection of spheres having radii from the centers at which the satellites lie, the radii corresponding to the distances from the positions of the satellites. However, such a method to calculate the distance involves various factors that may cause errors, which preclude accurate calculation of the distance. Therefore, a least-square method is used to calculate the position of the receiver on the basis of the calculated distances from the plurality of satellites to the receiver. Such a method is described in, for example, Takeyasu Sakai, “GPS Gijutsu Nyumon (Introduction to GPS Technology) (pp. 36-41)”, Tokyo Denki Daigaku Shuppan, Feb. 28, 2003.